Field of the Invention The present invention relates generally to a system for detecting air in a fluid line, and more particularly to a clamp-on detector apparatus for detecting air in the fluid line between a medication infusion reservoir such as an IV bottle or bag and an IV injection set or a medication infusion pump, which detector works equally well with transparent, translucent, or opaque fluids and includes means for ensuring that the detection system is functioning normally.
There are two principal techniques used to administer a continuous flow of medication to a patient, with both techniques involving the administration of a therapeutic fluid from a fluid reservoir or container which is typically an IV bottle. First, medication may be delivered through a conventional IV system using a drip chamber with the injection being made into various IV tubes and the associated paraphernalia, with drop counters being used to meter the amount of fluid delivered. Alternatively, medication infusion pumps may be utilized to administer drugs to a patient in small, precisely metered doses at frequent intervals or, alternatively, in the case of some devices, at a low but essentially continuous rate. Infusion pump therapy is electronically controlled to deliver precise, metered doses at exactly determined intervals.
An essential function of a medication infusion system is to avoid the infusion of fluid containing air bubbles therein. While a small amount of air may be contained in the fluid to be infused in very small air bubbles, larger air bubbles present a real danger to the patient if infused. Although steps may be taken to monitor the fluid line downstream before it reaches the patient to ensure that substantially no air bubbles remain in the fluid which is to be infused, it is also essential to minimize the possibility of air bubbles being contained in fluid near the reservoir end of the infusion apparatus. The detection of air bubbles in all fluids which are to be infused is therefore a critical design requirement.
The introduction of air into the infusion system near the reservoir happens principally when the IV bottle is empty. If the system remains unattended when the fluid reservoir or container is empty, air may be allowed to enter the fluid lines from the reservoir or container end. If no air-in-line detection apparatus is utilized, there is a real danger that IV systems could allow air in the infusion lines. In the case of systems using infusion pumps, even if the pump has an air-in-line detection apparatus, it is generally on the patient side of the pump. This would allow air to reach the infusion pump, and many infusion pumps will not pump air but rather will require repriming.
Many air-in-line detectors known in the art will work with either opaque fluids or with transparent fluids, but require a manual control to be set to the type of fluid being infused. Such detectors rely on the operator to set the control properly, and an operator error could result in the system not working properly and allowing air to pass through the fluid lines without providing an alarm. A detector which will automatically work on either opaque or transparent fluids is disclosed in U.S. Pat. No. 4,114,144, to Hyman. The Hyman detector first detects what type of fluid is in the line, and then provides an alarm if air enters the line.
While the Hyman detector represents an improvement on manual air-in-line detectors, it sacrifices simplicity for its automatic operation, requiring five sets of optical detectors to perform its function. Not only is the Hyman device fairly complex, but it is necessarily relatively larger and more expensive to manufacture than desirable. As may be see from the Hyman reference, the device is a built-in detector rather than an accessory detector, and is used (in the preferred embodiment) downstream of a pump. Due to its size, it is not readily useable as a standalone device, or as an empty container detector.
It is therefore the primary objective of the present invention to provide an empty container detection system for use either a conventional IV system or in conjunction with an infusion pump unit. The system of the present invention must be simple and easy to use, and must clamp onto a fluid line immediately downstream from the fluid reservoir or container. The empty container detection system of the present invention must be capable of immediately, accurately, and effectively detecting air in the fluid line regardless of whether the fluid being infused is opaque or transparent. The system must be fully automatic, not requiring any setup or intervention by an operator except clipping the device onto a line and plugging it in to the main pump unit or other controller.
Several other additional features are desirable in the design of the empty container detection system. One such feature is the ability to detect air bubbles whether the flow rate of the fluid in the line is fast or slow. In addition to being able to detect air in the fluid line, the system must also be accurate, presenting a high degree of resistance to false alarms. Since the detector of the system is to clip onto the fluid line, it must be small and light in size.
Despite the inclusion of all of the aforesaid features, the system of the present invention shall utilize a minimum number of parts, all of which parts are of inexpensive construction, yet which afford the empty container detector system of the present invention the high degree of accuracy which must be retained. The system of the present invention must also be of a design which enables it to compete economically with known competing systems, and it must provide an ease of use rivaling the best of competing systems. The system must accomplish all these objects in a manner which will retain and enhance all of the advantages of reliability, durability, and safety of operation. The system of the present invention must provide all of these advantages and overcome the limitations of the background art without incurring any relative disadvantage. All the advantages of the present invention will result in a empty container detector having a number of advantages making it a highly desirable alternative to systems presently available.